I Have No Idea How This Man-Cut-in-Half Prank Was Done

I have to hand it to Andy Gross: Not only is this man-cut-in-half prank completely hilarious, I'm also not completely sure how it's done. The best I can come up with is that the upper torso we see here is some kind of fake used to hide that he's really standing on his own two legs. Or maybe the whole thing is staged and his lower torso just has green tights that are edited out.